Understand recursion and pointers, and completely ace a data structures / algorithms class; having a decent grasp of combinatorics is very helpful, too. The coding challenges I give in interviews are almost always something like "here's a trivial game, write an algorithm to solve it optimally", which usually involves recursion, some sort of simple data structure, and combinations. Strong candidates solve these in about an hour (we allow 1.5 hours).

If you really like writing code, but you're not really into the science / math aspect, then I would suggest that you find something you're passionate about outside of development and then supplement that with your coding skills. But if you see your future as a solid developer, then I highly recommend that you at least take a data structures & algorithms course and definitely do as much work on the side as you can, because the real experience comes from tinkering around.

In-browser code editors that typically save your code on remote servers.

haha :) as a manager, i still keep up to date and contribute code in our team. i frequent programming challenge sites and keep testing myself, writing apps on my own, that sort of thing. complacency has no place in life, but especially not in development.

When you take leadership over a project and can envision its design from start to finish, and you can actually code it up in pretty much any language you'd like, you've made it. But then there's so much more to learn. So many sub-domains, so many new technologies.. there's the problem-solving component and the learning component. One should never rest on their laurels in this field unless you're just ready to be obsolete or you're ready for a career change. Any programmer worth their salt can pick up any language in very little time, but it takes discipline and practice to keep these skills relevant and sharp. A senior developer does all of this and has the willingness to learn more, apply fast, and thrive in any environment at a leadership capacity.

When I learned c++, I would use constructors and destructors, but never really cared about a copy constructor or an assignment operator. Meh, it worked for me, but I appreciate the principle today.